It's the summer months, and both my brother and I are home from college for the time being. This means we're currently sharing a wireless network.

We tried to play a game of Team Fortress 2 together this evening, and failed miserably; Without exception, the instant I tried to connect to the same server as him (or he, me) the other party would instantly disconnect.

Given that we have been able to play together on the same wireless network in the past (back around the WAR! Update), I was curious as to whether something changed in TF2 that might prevent two users on the same wireless network from connecting to the same server simultaneously? Is this a server option or security measure of some sort?

Since you're both using wireless I would make sure that AP Isolation is disabled to start. Or something to that effect, that setting prevents users on the wireless to see the other machines, which could be the reason to why you are getting disconnected.

Depending on your router setup, you will need to go into the settings to change the configuration of your NAT section. Most of the time, a router out of the box should support this type of gaming.

Last resort would be to do a factory reset on your router (usually holding the reset button for more than 5 seconds with it on, then rebooting it.) If you have configured the router yourself you should know what to do here, but make sure you backup the current configuration before you do, just in case.

If you're still stuck, what router/access point do you have and do you have access to the interface for the device?

I don't think the router is the issue, because our network plays fine for other multiplayer games, such as League of Legends or even Spiral Knights through Steam.
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Raven Dreamer♦Jul 1 '11 at 21:56

1

Since you're mentioning TF2, can you bring up the console and see what (if any) error messages are shown when one of you gets kicked/dropped? To enable the console, you have to go into Options -> Keyboard -> Advanced Options. Usually it's bound to the ~ key after you enable it.
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SoreanJul 2 '11 at 6:11